Pros to being a Merchindise Driven Show?
 

There is absolutely no hiding that Kamen Rider...and Super Sentai... and just about every other Tokusatsu is a merchandise driven show and, for all the flaws that this entails, there has to be good things about being a show like that. To start us off, I'll say that I really enjoy the creative weapons and equipment that they have to come up with every year. Swords are a dime a dozen in just about any medium no matter where you are, so I'm pretty impressed with just how many different way they can make such a common weapon unique.

Designs have to be more creative. When they reuse a motif (Beetles especially), they have to make them far different in comparison to past characters. It doesn't run into the problem a lot of action anime, especially shonen (Which, generally, aren't toy driven) has where everyone looks like everyone else.

It does require the show to add in periodic upgrades which, when done well, can keep the show fresh. I love the Showa era, but there is a feeling of monotony that can develop with no changes to the hero's power set or fighting style for 35+ episodes.

The shows have more creative touches with new forms etc.

It gives us a lot of cool stuff to look at. I personally love seeing all of the different suits.

What everyone else has said above with having cool stuff to look at and there is actually stuff I can buy. I hate how some shows have cool stuff that I want to buy but can't (*cough* Samurai Flamenco *cough*).

I think having to work around the stipulations of being merchandise driven can cause some really impressive creativity. Figuring out how to implement the weird ideas the Bandai higher-ups want you do, when done well, tends to make the show very unique.

From a story telling prospective, it forces the writers to find some kind of purpose for the toys they need to introduce and it's cool when they introduce something that helps expand the show's lore or mythos that they've created.

Easy example I can think of is the Lock Seeds.

Or they can do it like Kiva. :p

Another pro I think would be the fan's ability to immerse themselves in that particular fiction. If you enjoy these shows so much then when you buy the toys it suddenly becomes your show. You act out scenes that your imagination creates on the fly just by holding an action figure & a deluxe role-play item. That's great for children & I believe it can expand their creativity as much as the adults that write the very shows.